JUnitAdam Heath

What is JUnit?

JUnit is a unit testing framework for the Java programming language

It allows developers to swiftly and easily test parts of Java applications

It is part of the xUnit family of tools first designed by Kent Beck for the Smalltalk programming language

Unit Testing

Used for “Bottom Up” testing Test “units” of code Class → Test Class Orderless Tests written early Can be automated Ran often

JUnit Assertions

All asserts have an optional first argument 'message' which would be output on failure

assertArrayEquals(x, y)

assertEquals(x, y)

assertFalse(boolean)

assertTrue(boolean)

fail()

assertNull(object)

assertNotNull(object)

assertSame(object)

assertNotSame(object)

assertThat(x, Matcher)

JUnit Testing

public class Maths { private int[] arr; private int count, total;

// constructor, initiate to zero public Maths();

//Divide two numbers public static double divide(int a, int b);

//Add integers to sum public void addtosum(int a);

//Get the average public double average();

//Get the array storing our integers public int[] getArr();}//end class Maths

JUnit Testing

import org.junit.* ;public class MathsTest { @Test public void test_divide() { assertEquals(Maths.divide(4,2), 2.0) ; assertEquals(Maths.divide(2,4), 0.5) ; } @Test(expected=DivideByZeroException.class) public void test_divideZero() { Maths.divide(4,0); } @Test public void test_addtosum() { Maths m = new Maths(); m.addtosum(4); int[] expected = { 4 }; assertArrayEquals(expected, m.getArr()) m = null; }

JUnit Testing

@Test public void test_addtosumMore() { Maths m = new Maths(); m.addtosum(9878); m.addtosum(0); int[] expected = { 9878, 0 }; assertArrayEquals(expected, m.getArr()) m = null; }

@Test public void test_average() { Maths m = new Maths(); m.addtosum(5); m.addtosum(8); m.addtosum(23); m.addtosum(1); assertEquals(m.average(), 9.25) ; m = null; } }//class

JUnit Fixtures

@before public void beginMaths() { Maths m = new Maths(); } @after public void endMaths() { m = null; }

Fixtures allow us to define methods to be run before and after every test in that class

We can also use @BeforeClass and @AfterClass annotations

JUnit Fixtures

@before public void beginMaths() { Maths m = new Maths(); } @after public void endMaths() { m = null; }

@Test public void test_addtosum() { m.addtosum(4); int[] expected = { 4 }; assertArrayEquals(expected, m.getArr()) }

This test would run:beginMaths()test_addtosum()endMaths()

Running JUnit

Junit should be added to Java CLASSPATH

Text interface

java org.junit.runner.JUnitCore MathsTest

GUIs are available Integrated into IDE

Advantages

Fast Early discovery of errors Bug fixing Regression testing Time saved in testing Can help with design Can help to document the system

Disadvantages

Developer overhead Does not deal with Integration or Customer

testing Tests must be kept up to date Must be ran often

Questions?